Abstract

Recent studies underscore important roles of intestinal microbiota and the bacterial lipopolysaccharides (LPS) production in the pathogenesis of liver disease. However, how gut microbiota alters in response to the development of steatosis and subsequent progression to nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC) remains unclear. We aimed to study the gut microbial changes over liver disease progression using a streptozotocin-high fat diet (STZ-HFD) induced NASH-HCC C57BL/6J mouse model that is highly relevant to human liver disease. The fecal microbiota at various liver pathological stages was analyzed by 16S rDNA gene pyrosequencing. Both UniFrac analysis and partial least squares-discriminant analysis showed significant structural alterations in gut microbiota during the development of liver disease. Co-abundance network analysis highlighted relationships between genera. Spearman correlation analysis revealed that the bacterial species, Atopobium spp., Bacteroides spp., Bacteroides vulgatus, Bacteroides acidifaciens, Bacteroides uniformis, Clostridium cocleatum, Clostridium xylanolyticum and Desulfovibrio spp., markedly increased in model mice, were positively correlated with LPS levels and pathophysiological features. Taken together, the results showed that the gut microbiota was altered significantly in the progression of liver disease. The connection between the gut microbial ecology and the liver pathology may represent potential targets for the prevention and treatment of chronic liver disease and HCC.

The overall gut microbiota structure change and taxonomic and functional variations in the mouse gut microbiota

A. and C. A principal-coordinates (PCoA)-based characterization of overall community structure for mice from control group and STZ-HFD group at all-time points. QIIME was used to compute microbial β diversity with the unweighted (A) and weighted (C) UniFrac analysis. Sample similarities were projected onto two dimensions using principal coordinates. B. and D. Clustering of gut microbiota based on distances between the groups, calculated by multivariate analysis of variance tests of the first 48 PCs of unweighted (B) and weighted (D) UniFrac distance and conducted using DendroUPGMA. Cophenetic correlation coefficient value was 0.89 and 0.91, respectively. E. Relative abundance of major phyla across 48 fecal microbiota from mice in control. F. Relative abundance of major phyla across 48 fecal microbiota from mice in STZ-HFD group.

SparCC network plot of co-abundance and co-exclusion correlations between OTUs

Nodes represent OTUs involved in either significant co-abundance (red edges) or co-exclusion (blue edges) relationships, with the magnitude of the correlation expressed as the intensity of the respective edge colors. The color of each node indicates the genus of the OTUs. Only significant correlations (two-sided pseudo p ≤ 0.05 based on bootstrapping of 100 repetitions) with an absolute correlation magnitude ≥0.6 are presented.